Method and device for offset-voltage free voltage measurement and adjustment of a reference voltage source of an integrated semiconductor circuit

ABSTRACT

A method and device for measuring voltage of an internal reference voltage source of an integrated semiconductor circuit, in particular, a DRAM, including the steps of comparing a reference voltage to an external comparison voltage with a comparator, forming a measured value for the reference voltage to be set in accordance with a comparison result, switching a commutator by a clock- or software-control to alternatively apply the reference voltage and the comparison voltage to the comparator inputs at the same time, varying one of the reference and comparison voltage to a setpoint voltage value until the comparator output changes its logic value at each commutator switched stage, buffering the voltage values present for each switched state when the logic value changes, forming an average value for the reference voltage from the stored voltage values, and setting the reference voltage as a function of the average value formed.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a method and a device for measuring/adjusting avoltage of an internal reference voltage source of an integratedsemiconductor circuit, in particular, of a dynamic semiconductor memory.The reference voltage to be measured is compared by a comparator with acomparison voltage supplied from the outside, and the measurement resultis formed in accordance with the result of the comparison.

German Patent DE 199 60 244.1 describes a configuration for trimmingreference voltages in semiconductor chips.

In particular, in the case of integrated memory modules, for example,dynamic semiconductor memories (DRAMs) it is necessary to adjust or trimthe setpoint voltage of voltage generators located on the chip, whichfluctuates due to fabrication tolerances. According to the current stateof the art in circuit technology, it is not possible to make availablesuch voltage on the chip with greater precision than ±10% without anadjusting or trimming procedure.

However, before such a trimming or adjusting procedure can be carriedout, the chip-internal reference voltage must be measured.

In order to improve the measuring accuracy, the reference voltage iscurrently measured using an external test system. The voltage can bevaried in a specific range using software registers. The suitable valuesin the registers are determined from the measured value in the testsystem to arrive at the correct internal voltage, and the suitablevalues can be burnt into the chip permanently by laser fuses.

Such a method contributes considerably to the test costs: during themeasurement of the internal reference voltage of SDRAM modules,sixty-four (64) modules, for example, are measured in parallel perwafer. Thus, it is necessary to determine sixty-four (64) analogousvoltages with a high degree of accuracy by the test system. In the caseof embedded DRAMs, there are a plurality of reference voltages on onemodule, for example, eight (8) reference voltages. Experience has shownthat considerable fluctuations in reference voltages also occur withinthe module. In such a case, eight (8) analogous reference voltages mustbe measured per module.

With the concept proposed in German Patent DE 199 60 244.1 specifiedabove, it is possible to standardize an internal voltage by making aninternal digital/analog converter run through various values of acorrection voltage.

In addition, it is possible to measure an internal voltage by searchingfor an external voltage that corresponds to the internal referencevoltage. For such a method, just one binary output has to be led outfrom the chip. To compare the external voltage supplied from the outsidewith the internal reference voltage, an operational amplifier serving asa comparator must have a very high degree of accuracy because the offsetvoltage is completely absorbed in the set value for the referencevoltage.

However, in customary operational amplifiers (in particular, CMOSoperational amplifiers), it is possible, without a large degree ofexpenditure on circuitry, for considerable offset voltages to occur thatare known to be the consequence of parameter variation in thetransistors of the amplifier. If it is desired to minimize suchparameter variations, the operational amplifier becomes very complex andcostly.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a method anddevice for offset-voltage-free voltage measurement and adjustment of areference voltage source of an integrated semiconductor circuit thatovercomes the hereinafore-mentioned disadvantages of theheretofore-known methods and devices of this general type and thatavoids the described problem of the offset voltage of the detectingoperational amplifier so that a cost-effective operational amplifier canbe used.

With the foregoing and other objects in view, there is provided, inaccordance with the invention, a method for measuring and setting of avoltage of an adjustable internal reference voltage source of anintegrated semiconductor circuit including the steps of comparing areference voltage to an external comparison voltage with a comparatorhaving two inputs, forming a measured value for the reference voltagethat is to be set in accordance with a result of the comparison,switching a commutator by one of a clock-control and a software-controlto alternatively apply the reference voltage and the external comparisonvoltage to the two inputs of the comparator at the same time, varyingone of the reference voltage and the external comparison voltage in adirection of a setpoint voltage value until the comparator outputchanges its logic value at each switched stage of the commutator,buffering the voltage values present for each switched state of thecommutator when the logic value of the comparator output changes andrespectively varied in the preceding step, forming an average value forthe reference voltage from the stored voltage values, and setting thereference voltage as a function of the average value formed in thepreceding step. Preferably, the integrated semiconductor circuit is adynamic semiconductor memory.

By the method according to the invention it is possible for the voltagevalue to be measured independently of the offset voltage of theoperational amplifier serving as the comparator, by virtue of the factthat a change-over switch or commutator is provided upstream of theoperational amplifier that functions as a comparator and the commutatoralternately applies the reference voltage to be measured and thecomparison voltage supplied from the outside to the comparator inputs.The measured value determined for the respective switched position ofthe commutator is stored in a piece of software that runs in a controlunit forming, for example, part of a test equipment unit, and an averagevalue is formed from the measured value. Thus, by software, the problemof the offset voltage of the comparator is avoided.

The method according to the invention proposes that the offset problemsbe avoided by a software solution. As such, the offset voltage iscarried out by an offset elimination effectuated by software.

In accordance with another mode of the invention, it is also possibleand, in view of the unavoidable RC characteristics of an externalcomparison voltage, possibly advantageous to vary the externalcomparison voltage incrementally and to place the commutator orchange-over switch upstream of the comparator in both settings for eachvalue of the comparison voltage.

In accordance with a further mode of the invention, it is also possibleto fix the external comparison voltage at a setpoint value for theinternal voltage, and to vary the internal reference voltage.

In accordance with an added mode of the invention, the varying step iscarried out by maintaining the internal reference voltage constant whilevarying the external comparison voltage.

In accordance with an additional mode of the invention, the switchingand varying steps are performed by, in a first switched state of thecommutator, firstly varying the external comparison voltage in a voltagerange around the setpoint voltage value with the reference voltage keptconstant, and performing the buffering step by buffering that voltagevalue of the external comparison voltage at which the comparator outputchanges its logic state, and, in the second switched state of thecommutator in which the reference voltage and the external comparisonvoltage are interchanged between the two comparator inputs in comparisonwith the first switched state of the commutator, varying the externalcomparison voltage in a voltage range around the setpoint voltage valuewith the reference voltage kept constant, and performing the bufferingstep by storing that voltage value of the external comparison voltage atwhich the comparator output changes its logic state.

In accordance with yet another mode of the invention, the externalcomparison voltage is incrementally varied.

In accordance with yet a further mode of the invention, the two switchedstates and of the commutator are assumed for each voltage value of theexternal comparison voltage.

In accordance with yet an added mode of the invention, the externalcomparison voltage is kept constant at a setpoint value for the internalreference value while the internal reference voltage is varied.

In accordance with yet an additional mode of the invention, theswitching and varying steps are performed by, in a first switched stateof the commutator, varying the reference voltage in a voltage rangearound the voltage value of the external comparison voltage that is keptconstant with the external comparison voltage kept constant, andperforming the buffering step by storing that voltage value of thereference voltage at which the comparator output changes its logicstate, and, in the second switched state of the commutator, varying thereference voltage in a voltage range around the voltage value of theexternal reference voltage that is kept constant with the externalcomparison voltage kept constant, and performing the buffering step bystoring that voltage value of the internal reference voltage at whichthe comparator output changes its logic state.

In accordance with again another feature of the invention, the internalreference voltage is incrementally varied.

With the objects of the invention in view, there is also provided adevice for carrying out the method for measuring and setting of avoltage of an adjustable internal reference voltage source of anintegrated semiconductor circuit including an internal reference voltagesource providing an internal reference voltage, an external comparisonvoltage source providing an external comparison voltage, a comparatorhaving two comparator inputs, a commutator having two commutator inputsand two commutator outputs, each of the two commutator inputs connectedto a respective one of the internal reference voltage source and theexternal comparison voltage source, and each of the two commutatoroutputs directly connected to the two comparator inputs, the commutatoralternately switching the two comparator inputs between the internalreference voltage and the external comparison voltage.

In accordance with again a further feature of the invention, there isprovided a control unit connected to the commutator for switching thecommutator

In accordance with again an added feature of the invention, the programproposed for software-supported offset elimination resides preferably ina control unit that also switches the commutator into the two settings.

It is advantageous that only a small portion of the components necessaryfor the voltage measurement have to be located on the chip. As such, inaccordance with again an additional feature of the invention, at leastthe commutator and the comparator are provided on the chip of theintegrated memory module. As mentioned, the comparator can beimplemented by a cost-effective operational amplifier that takes uplittle chip area.

In accordance with still another feature of the invention, the controlunit can be implemented as a program-controlled processor unitprogrammed to store the voltage values present for each switched stateof the commutator and to form an average value for the reference voltagefrom the stored voltage values.

Preferably, in accordance with still further features of the invention,the processor unit has a storage device or means for storing the voltagevalues, and/or an average value forming device or means for forming anaverage value for the reference voltage from the stored voltage values.

In accordance with still an added feature of the invention, the controlunit is preferably part of an external test equipment unit or measuringequipment unit for testing the integrated semiconductor circuit.

With the objects of the invention in view, there is also provided adevice for measuring and setting of a voltage of an adjustable internalreference voltage source of an integrated semiconductor circuit, inparticular, a dynamic semiconductor memory, including an internalreference voltage source providing an internal reference voltage, anexternal comparison voltage source providing an external comparisonvoltage, a comparator having two comparator inputs and a comparatoroutput for outputting a logic value, a commutator having switchedstages, a switch input, two commutator inputs, and two commutatoroutputs, each of the two commutator inputs connected to a respective oneof the internal reference voltage source and the external comparisonvoltage source, each of the two commutator outputs directly connected toa respective one of the two comparator inputs, the commutatoralternately switching the two comparator inputs between the internalreference voltage and the external comparison voltage, the comparatorcomparing the internal reference voltage to the external comparisonvoltage, a switch control having a switch output connected to the switchinput of the commutator for alternatively applying the internalreference voltage and the external comparison voltage to the twocomparator inputs at the same time, and one of the internal referencevoltage and the external comparison voltage are varied in a direction ofa setpoint voltage value until the comparator output changes the logicvalue at each switched stage of the commutator.

In accordance with still an additional feature of the invention, acontrol unit is configured to form a measured value for the internalreference voltage that is to be set in accordance with a result of acomparison of the comparator, to buffer voltage values present for eachof the switched states of the commutator when the logic value changesand the one of the internal reference voltage and the externalcomparison voltage is varied, to form an average value for the internalreference voltage from stored voltage values, and to set the internalreference voltage as a function of the average value formed.

In accordance with a concomitant feature of the invention, the switchcontrol is a clock-control or a software-control

With the features described above, the invention has in particular thefollowing advantages:

The internal reference voltage can be measured independently of theoffset voltage of the detecting operational amplifier and, subsequently,given a permanent setting. The error that occurs here in the voltagemeasurement can easily be kept within the submillivolt range.

The operational amplifier used is cheap and takes up only a small chiparea.

The self-alignment logic can be tested because the data polarity has tobe different depending on the position of the polarity switch.

As a result of the offset-tolerant method of voltage measurement, a highcommon mode range of the operational amplifier that serves as acomparator can be utilized.

Other features that are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a method and device for offset-voltage-free voltage measurement andadjustment of a reference voltage source of an integrated semiconductorcircuit, it is, nevertheless, not intended to be limited to the detailsshown because various modifications and structural changes may be madetherein without departing from the spirit of the invention and withinthe scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block circuit diagram of a first exemplary embodiment of ameasuring device according to the invention;

FIG. 1B is a block circuit diagram of a control unit for the embodimentof FIG. 1;

FIG. 2 is a flowchart of a sequential program in the control unit ofFIG. 1B;

FIG. 3A is a block circuit diagram of a second exemplary embodiment of ameasuring device according to the invention;

FIG. 3B is a block circuit diagram of a control unit for the secondexemplary embodiment of FIG. 3A; and

FIG. 4 is a flowchart of an alternative sequential program for carryingout the measuring method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In all the figures of the drawing, sub-features and integral parts thatcorrespond to one another bear the same reference symbol in each case.

Referring now to the figures of the drawings in detail and first,particularly to FIG. 1A thereof, there is shown, in the form of a blockcircuit diagram, a commutator 1 that is provided for switching thevoltages to be applied to the two inputs (+, −) of a comparator 2,namely a chip-internal reference voltage (Vint) to be measured and acomparison voltage (Vext) that is supplied from the outside for such apurpose.

An embodiment is illustrated in which the commutator 1 is switched usinga clock signal CLK so that the commutator 1 respectively assumes oneswitched setting and the other switched setting during the high and lowlevel phases of the clock signal CLK. The output K of the comparator 2is connected to an EX-OR element 3 to which the clock signal CLK is alsosupplied. The flowchart that is described below and illustrated in FIG.2 and that relates to the execution of the measuring procedure accordingto the invention resides in a control unit 6 (FIG. 1B) that ispreferably set up as a program-controlled processor unit and receivesthe output signal Dout of the EX-OR element 3 at the input end andoutputs the external comparison voltage Vext and the measurement resultVaver for the internal reference voltage (Vint) to be measured, at theoutput end.

An exemplary measuring method will now be described with reference tothe flowchart illustrated in FIG. 2. First, the commutator 1 is placedin setting A (steps S0 to S3) after the start of the program,initialization of the semiconductor module to be measured (for exampleDRAM), activation of the test mode, switching on of the comparator 2 andafter the external comparison voltage Vext has been applied to thecommutator 1. If the commutator 1 is placed in setting A in step S3, itis possible to proceed such that, first, the external comparison voltageVext specifies the lowest expected voltage value for the referencevoltage Vint to be measured. Alternatively (not illustrated in FIG. 2),the external comparison voltage Vext can specify the maximum voltagevalue of the reference voltage Vint to be measured.

An interrogation in step S4 interrogates, by the output signal Dout ofthe EX-OR element 3, whether or not the output K of the comparator 2changes its logic value. Such a change is the case under the conditionpredefined in step S3 as soon as Vext has become greater than Vint. Aslong as the output K of the comparator 2 does not change its logicvalue, Vext is increased by a voltage increment DV. For theabove-mentioned alternative procedure, if Vext specifies the maximumexpected value of the reference voltage Vint to be measured, there wouldbe an interrogation in interrogation step S4 to determine whether or notVext has become smaller than Vint, and if such is not the case, Vext isreduced incrementally by the increment DV in step S5.

If the interrogation step S4 supplies a yes result, the present value ofVext is stored as the value Vext, A for the commutator setting A (stepS6).

Then, in step S7 the commutator is placed in setting B, in which the twoinput voltages at the comparator inputs are interchanged (step S7), andthe further steps S8-S10 then proceed analogously to the steps S4-S6.Here too, the alternative procedure described above can also beselected, namely that Vext specifies the maximum expected voltage of theinternal reference voltage Vint in step S7. Finally, in step S11 themeasured value for the reference voltage Vint to be measured is formedby forming arithmetic averages of the voltage values Vext, A and Vext, Brespectively stored in steps S6 and S10. After the routine in FIG. 2(step S12) has ended, Vint=Vaver can then be permanently set.

FIGS. 3A and 3B show, in the form of a block circuit diagram, analternative measuring device according to the invention in which, incontrast with the device shown in FIGS. 1A and 1B, the externalcomparison voltage Vext is permanently predefined as the setpoint valuefor the reference voltage Vint to be measured, i.e., the internalreference voltage Vint that is to be set, and Vint is varied. The changein the internal reference voltage Vint takes place under clock controlby a counter 4 and a digital/analog converter 5 whose output suppliesthe analogous reference voltage Vint and feeds it to one of the inputsof the commutator 1. The other input of the commutator 1 has theconstant external comparison voltage Vext applied to it. The counter 4is preset by the control unit 6 to a preset value that corresponds to anexpected value for Vint. The counter readings ZA and ZB relating to thecommutator settings A and B are then respectively determined andbuffered in a register 7 and a register 8. An average value former 9determines the offset-voltage-corrected counter reading (ZA+ZB)/2 fromthe counter readings ZA and ZB buffered in the registers 7 and 8. Thehalving is carried out by index displacement. As such, the correct valuefor the internal reference voltage Vint can be determined (measured) byadding simple hardware components 4, 5 and 7 to 9, which take up littlespace, to the comparator 1 and the commutator 2 on the semiconductorchip. The program that is to be provided in the control unit 6 iscorrespondingly simplified.

FIG. 4 shows, in the form of a flowchart, an alternative procedure formeasuring Vint if the external comparison voltage Vext is varied, thatis to say based on the block circuit diagram shown in FIGS. 1A and 1B.

Whereas the steps S20 to S23 and S34 of a flowchart in FIG. 4 eachcorrespond to the steps S0 to S3 and S11 of the program sequenceaccording to FIG. 2, the voltage Vext is varied incrementally in stepsS24 to S33, and the commutator 1 is placed in both settings for eachvalue of Vext. In the program sequence illustrated in FIG. 4 it is alsopossible to adopt the alternative procedure, in the same way as has beendescribed above for the program sequence illustrated in FIG. 2, thatVext is predefined as the maximum expected value of the internalreference voltage Vint, and is then incrementally reduced by DV.

It is to be noted that, instead of one comparator 2, as is contained inthe exemplary embodiments illustrated in FIGS. 1A and 3A, twocomparators can also be easily used to increase the common mode range.

The invention described above enables the self-alignment method foradjusting the correct reference voltage of a semiconductor chip to becarried out easily independently of the offset voltage of an operationalamplifier used as a comparator, so that the requirements of theoperational amplifier with respect to the offset voltage can be reduced.

The voltage value determined by the measuring method according to theinvention described above can then be used to set the correct voltagevalue to operate the semiconductor chip by, for example, the methoddescribed in the above-mentioned German Patent DE 199 60 244.1 by firingor burning in fuses selected by an address generator.

We claim:
 1. A method for measuring and setting of a voltage of anadjustable internal reference voltage source of an integratedsemiconductor circuit, the method which comprises: a. providing areference voltage from the internal reference voltage source and anexternal comparison voltage to a respective one of two voltage inputs ofa commutator having two voltage outputs and being alternativelyswitchable to a first and a second commutating state via one of a clocksignal and a switching signal from a control unit, both signals beingapplied to a clock input of the commutator; b. switching the commutatorto the first commutating state; c. applying, in the first commutatingstate, at the same time, via the voltage outputs of the commutator, thereference voltage and the external comparison voltage, respectively to afirst and second input of a comparator having an output; d. comparingthe reference voltage and the external comparison voltage via thecomparator in first commutating state; e. varying, via the control unit,one of the reference voltage and the external comparison voltage in adirection of a setpoint voltage value of one of the reference voltageand the external comparison voltage until the control unit detects achanging logic value of the comparator output; f. buffering, via thecontrol unit, the voltage value varied in the preceding varying step andpresent for the current commutation state of the commutator upon thecontrol unit detecting the changing logic value of the comparatoroutput; g. switching the commutator to the second commutating state; h.applying, in the second commutating state, at the same time thereference voltage and the external comparison voltage via the voltageoutputs of the commutator, respectively to the first and the secondinput of the comparator; i. comparing, in the second commutating state,the reference voltage and the external comparison voltage via thecomparator; j. repeating steps e and f; k. forming, via the controlunit, an average value for the reference voltage from the bufferedvoltage values; and l. setting the reference voltage as a function ofthe average value formed in the preceding step.
 2. The method accordingto claim 1, wherein the control unit performs the varying step bymaintaining the internal reference voltage constant while varying theexternal comparison voltage.
 3. The method according to claim 2, whereinthe control unit incrementally varies the external comparison voltageand clocks or switches the commutator to assume the two commutatingstates of the commutator for each voltage value of the externalcomparison voltage.
 4. The method according to claim 1, wherein thecontrol unit performs the step of switching the commutating state andvarying step by: in the first commutating state of the commutator,firstly varying the external comparison voltage in a voltage rangearound the setpoint voltage value with the reference voltage keptconstant, and performing the buffering step by buffering that voltagevalue of the external comparison voltage at which the comparator outputchanges its logic state; and in the second commutating state of thecommutator in which the reference voltage and the external comparisonvoltage are interchanged between the two comparator inputs in comparisonwith the first commutating state of the commutator, varying the externalcomparison voltage in a voltage range around the setpoint voltage valuewith the reference voltage kept constant, and performing the bufferingstep by storing that voltage value of the external comparison voltage atwhich the comparator output changes its logic state.
 5. The methodaccording to claim 4, which-comprises incrementally varying the externalcomparison voltage with the control unit.
 6. The method according toclaim 1, wherein the control unit incrementally varies the externalcomparison voltage and assumes the two commutating states of thecommutator for each voltage value of the external comparison voltage. 7.The method according to claim 1, which further comprises maintaining theexternal comparison voltage constant at a setpoint value for theinternal reference value while varying the internal reference voltage.8. The method according to claim 7, which further comprises performingthe switching and varying steps by: in a first switched state of thecommutator, varying the reference voltage in a voltage range around thevoltage value of the external comparison voltage that is kept constantwith the external comparison voltage kept constant, and performing thebuffering step by storing that voltage value of the reference voltage atwhich the comparator output changes its logic state; and in the secondswitched state of the commutator, varying the reference voltage in avoltage range around the voltage value of the external reference voltagethat is kept constant with the external comparison voltage keptconstant, and performing the buffering step by storing that voltagevalue of the internal reference voltage at which the comparator outputchanges its logic state.
 9. The method according to claim 8, whichfurther comprises incrementally varying the internal reference voltage.10. A device for carrying out the method according to claim 1,comprising: an internal reference voltage source providing an internalreference voltage; an external comparison voltage source providing anexternal comparison voltage; a comparator having two comparator inputs;a commutator having two commutator inputs and two commutator outputs;each of said two commutator inputs connected to a respective one of saidinternal reference voltage source and said external comparison voltagesource; and each of said two commutator outputs directly connected tosaid two comparator inputs, said commutator alternately switching saidtwo comparator inputs between said internal reference voltage and saidexternal comparison voltage.
 11. The device according to claim 10,including a control unit connected to said commutator for switching saidcommutator.
 12. The device according to claim 10, wherein: theintegrated semiconductor circuit is part of a chip; and at least saidcommutator and said comparator are provided on the chip.
 13. The deviceaccording to claim 11, wherein said control unit is a program-controlledprocessor unit programmed: to store the voltage values present for eachswitched state of the commutator; and to form an average value for thereference voltage from the stored voltage values.
 14. The deviceaccording to claim 13, wherein said processor unit has a means forstoring the voltage values.
 15. The device according to claim 13,wherein said processor unit has a means for forming an average value forthe reference voltage from the stored voltage values.
 16. The deviceaccording to claim 13, wherein said processor unit has a storage devicefor storing the voltage values.
 17. The device according to claim 13,wherein said processor unit has an average value forming device forforming an average value for the reference voltage from the storedvoltage values.
 18. The device according to claim 14 wherein: anexternal testing device tests the integrated semiconductor circuit; andsaid control unit is part of the external testing device.
 19. A devicefor measuring and setting of a voltage of an adjustable internalreference voltage source of an integrated semiconductor circuit,comprising: an internal reference voltage source providing an internalreference voltage; an external comparison voltage source providing anexternal comparison voltage; a comparator having two comparator inputsand a comparator output for outputting a logic value; a commutatorhaving switched stages, a switch input, two commutator inputs, and twocommutator outputs; each of said two commutator inputs connected to arespective one of said internal reference voltage source and saidexternal comparison voltage source; each of said two commutator outputsdirectly connected to a respective one of said two comparator inputs;said commutator alternately switching said two comparator inputs betweensaid internal reference voltage and said external comparison voltage;said comparator comparing said internal reference voltage to saidexternal comparison voltage; a switch control having a switch outputconnected to said switch input of said commutator for alternativelyapplying said internal reference voltage and said external comparisonvoltage to said two comparator inputs at the same time; and one of saidinternal reference voltage and said external comparison voltage arevaried in a direction of a setpoint voltage value until said comparatoroutput changes said logic value at each switched stage of saidcommutator.
 20. A method for measuring and setting of a voltage of anadjustable internal reference voltage source of a dynamic semiconductormemory, which method comprises: comparing a reference voltage to anexternal comparison voltage with a comparator having two inputs;switching a commutator by one of a clock signal and a switching signalapplied from a control unit to a clock input terminal of the commutatorto alternatively switch the commutator between a first and a secondcommutating state to alternatively apply the reference voltage suppliedfrom the dynamic semiconductor memory and the external comparisonvoltage supplied from the control unit to the two inputs of thecomparator at the same time, the commutator having two voltage inputterminals for respectively receiving the reference voltage and theexternal comparison voltage and two voltage output terminals forsupplying the alternately two switched input voltages; varying with thecontrol unit one of the reference voltage and the external comparisonvoltage in a direction of a setpoint voltage value of one of thereference voltage and the external comparison voltage until thecomparator output changes its logic value at each switched stage of thecommutator; buffering with the control unit the voltage valuesrespectively varied in the preceding varying step and present for eachcommutating state of the commutator when the logic value of thecomparator output changes; forming with the control unit an averagevalue for the reference voltage from the stored voltage values; andsetting the reference voltage in the dynamic semiconductor circuit as afunction of the average value formed in the preceding forming step. 21.The device according to claim 19, including a control unit configuredto: to form a measured value for said internal reference voltage that isto be set in accordance with a result of a comparison of saidcomparator; to buffer voltage values present for each of said switchedstates of said commutator when said logic value changes and said one ofsaid internal reference voltage and said external comparison voltage isvaried; to form an average value for said internal reference voltagefrom stored voltage values; and to set said internal reference voltageas a function of said average value formed.
 22. The device according toclaim 19, wherein said switch control is a clock-control.
 23. The deviceaccording to claim 19, wherein said switch control is asoftware-control.
 24. A device for measuring and setting of a voltage ofan adjustable internal reference voltage source of a dynamicsemiconductor memory, comprising: an internal reference voltage sourceproviding an internal reference voltage; an external comparison voltagesource providing an external comparison voltage; a comparator having twocomparator inputs and a comparator output for outputting a logic value;a commutator having switched stages, a switch input, two commutatorinputs, and two commutator outputs; each of said two commutator inputsconnected to a respective one of said internal reference voltage sourceand said external comparison voltage source; each of said two commutatoroutputs directly connected to a respective one of said two comparatorinputs; said commutator alternately switching said two comparator inputsbetween said internal reference voltage and said external comparisonvoltage; said comparator comparing said internal reference voltage tosaid external comparison voltage; a switch control having a switchoutput connected to said switch input of said commutator foralternatively applying said internal reference voltage and said externalcomparison voltage to said two comparator inputs at the same time; andone of said internal reference voltage and said external comparisonvoltage are varied in a direction of a setpoint voltage value until saidcomparator output changes said logic value at each switched stage ofsaid commutator.